Bond coat with low deposited aluminum level and method therefore

Abstract

A method for applying a NiAl based bond coat and a diffusion aluminide coating to a metal substrate is disclosed. The method comprises providing a superalloy substrate, the superalloy substrate having an external surface; and optionally cleaning the external surface of the superalloy substrate. The method further comprises coating a portion of the external surface of the superalloy substrate, by physical vapor deposition with a layer of a NiAl based metal alloy, wherein the deposited NiAl based metal alloy includes a controlled amount of about 6 to 25 weight percent aluminum and additionally the deposited aluminum level of the NiAl based metal alloy is controlled to be about 50-100% of its final level after aluminizing to form a coated external portion; and subsequently, simultaneously aluminizing the coated external portion and a different surface of the superalloy substrate. Advantageously, a diffusion aluminide layer is formed on the different surface and the NiAl based metal alloy becomes a NiAl based bond coat, wherein the NiAl based bond coat comprises between about 12 to 25 weight percent aluminum, and the NiAl based bond coat has a uniform distribution of aluminum and other modifying elements selected from at least one of Cr, Zr and Hf throughout the NiAl based bond coat.

1 - 18 . (canceled) 
     
     
         19 . A gas turbine engine component comprising:
 a superalloy substrate having an external surface, wherein a portion of the external surface is coated with a layer of a NiAl based metal alloy including a controlled amount of about 6 to 25 weight percent aluminum and additionally the deposited aluminum level of the NiAl based metal alloy is controlled to be about 50-100% of its final level after aluminizing, which is subsequently aluminized to simultaneously form a diffusion aluminide layer on a different surface of the superalloy substrate and a NiAl based bond coat on the portion of the external surface of the superalloy substrate, wherein the NiAl based bond coat comprises about 12 to 25 weight percent aluminum, and has a uniform distribution of aluminum and other modifying elements selected from at least one of Cr, Zr and Hf throughout the NiAl based bond coat.   
     
     
         20 . The gas turbine engine component of  claim 19 , wherein the different surface of the superalloy substrate, which is simultaneously aluminized along with the NiAl based metal alloy is selected from at least one of an external, underportion of a blade platform and an attachment hook of a shroud. 
     
     
         21 . The gas turbine engine component of  claim 19 , wherein the component is a turbine blade or a turbine vane. 
     
     
         22 . The gas turbine engine component of  claim 21 , wherein the NiAl base alloy source material has a composition, in approximate weight percent, of 19.53Al-6.37Cr-1.85Zr, balance Ni.